1. Field
This invention relates to a method and apparatus for use in aligning the wheels of an automobile and, in particular, a method and apparatus for indicating the orientation of an automobile wheel relative to the manufacturer's specifications for proper alignment throughout the alignment process.
2. Brief Description of the Prior Art
Due to the proliferation in recent years of front wheel drive cars, a problem has arisen regarding the proper alignment of the rear wheels of such cars. In order to provide background information s that the unique features of this invention may be completely understood and fully appreciated, the steps for performing a four-wheel alignment on a typical front wheel drive vehicle requiring such alignment should be described.
Initially, the existing readings for the camber, caster, and toe parameters for all four wheels are obtained with a conventional alignment machine. As is generally known in the art, camber refers to the outward or inward tilt of the wheel at the top, caster refers to the angle, in degrees, of the steering axis relative to a standard vertical axis, and toe represents the extent to which a leading edge of the wheel is biased inwardly (toe-in) or outwardly (toe-out) expressed in degrees, inches, or millimeters. Generally speaking, wheel alignment involves comparing these initial readings to the specifications established by the vehicle's manufacturer, then applying appropriate adjustment techniques until the actual readings correspond to the recommended specifications.
Of the front wheel drive cars requiring four-wheel alignment, approximately half require some form of modification or adaptation during the alignment procedure because these cars are manufactured with no provisions for future adjustment of camber, caster or toe. Therefore, on these vehicles, removal of the entire wheel assembly is necessary and/or desirable in order to align the wheel in accordance with the manufacturer's specifications. It is generally preferable to align the rear wheels first, then align the front wheels.
After the existing camber, caster, and toe readings are determined by a conventional alignment machine, the vehicle is raised on a jack or other suitable lift system wherein the alignment sensor, the rear wheel, and, in some cases, the brake drum and/or rotor are removed to allow the worker to remove the bolts securing the spindle/hub assembly to the axle. In most cases, a modifying implement, such as tapered shims, must be installed between the axle and spindle/hub assembly to correct camber and/or toe misalignment. After installation of the tapered shims (o other modifying accessories such as a tapered wedge or an eccentric bushing), the worker must reinstall the brake drum, wheel, and alignment sensors and then lower the vehicle in order to obtain new readings from the alignment machine. If the camber, caster, and/or toe settings require further adjustment, the entire procedure must be repeated until proper alignment is accomplished. Frequently, the procedure must be repeated several times before proper alignment is attained, at a time cost of approximately 20 minutes per attempt. This typical trial and error technique is extremely time consuming, monopolizes the alignment bay working area for an inordinate amount of time, and diminishes the profit margin of the business.
There are several types of conventional devices currently being marketed which are designed to assist in the wheel alignment procedure. One such device is the "knuckle leg" alignment device. This device comprises a fixture which is attached to the wheel hub after removal of the wheel from the vehicle. The "knuckle leg" is essentially a metal bracket used to support the vehicle weight once the wheel is removed, and embodies no alignment capabilities in and of itself. After an alignment sensor is attached to the "knuckle leg" device, alignment may be accomplished with the wheels removed, but only if the wheel hub itself does not have to be removed. To properly utilize this device, time and careful consideration must be given to remove both wheels of the same axle to assure that the vehicle maintains a level posture. Since the "knuckle leg" bolts to the wheel hub and supports the vehicle weight in the same manner as the vehicle wheel the device is neither time efficient nor particularly advantageous in applications which require wheel hub removal.
Another known device for assisting with wheel alignment is the magnetic adjustable camber gauge (part No. 813) manufactured by Specialty Products Company. This device, however, is designed to check only the camber reading and is unable to obtain toe and caster readings. Additionally, the magnetic mount utilized with the device covers only a one inch radius of a hub that is normally six to eight inches in diameter. This limited range of contact makes the gauge generally insufficient to ascertain reliable readings.
No known existing alignment apparatus achieves or fulfills the purposes of the present invention, namely, to accurately duplicate the camber, caster and toe readings received from an alignment machine and then obtain and monitor any changes which occur during the alignment process, eve though the vehicle is suspended with the wheels removed.